<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
   <div id="app">
    
   </div>
   <script src="https://unpkg.com/vue@2/dist/vue.js"></script>
   <script src="https://unpkg.com/vue-router@3/dist/vue-router.js"></script> 
   <script>
    var vm = new Vue({
        el:'#app',
        template:`<div>hello<component-a></component-a></div>`,
        components:{
            'component-a':{
                template:'<span>world</span>'
            }
        }
    });
   </script>
</body>
</html>